In these years, laser radar devices are more and more used for monitoring the surroundings of vehicles, buildings, and the like, and especially laser radar devices capable of performing wide angle scanning using two-dimensional scanners are gaining in popularity. In addition, in order to support operation and parking of a vehicle, a system that includes a plurality of laser radar devices mounted on the vehicle and that monitors all the surroundings of the vehicle has been proposed.
As an example of the related art, a technique has been disclosed in which a control unit that controls light-emitting timings of light-emitting sources in such a way as to provide light-emitting periods in which light is emitted to target space and off periods in which light is not emitted controls the light-emitting timings such that the light-emitting periods of the light-emitting sources of detection devices do not overlap. In addition, a technique has been disclosed in which it is determined that there is an obstacle only when the obstacle has been detected by at least two of four units, that is, a pair of laser light-emitting units and a pair of ultrasonic wave transmission units, provided on the front (or the back) of a vehicle in substantially the traveling direction of the vehicle. For example, these techniques are disclosed in Japanese Laid-open Patent Publication No. 2006-300616 and Japanese Laid-open Patent Publication No. 03-164345